Nonvolatile memory device and method of fabricating the same

ABSTRACT

The nonvolatile memory device includes a semiconductor substrate, a first and a second diffusion regions formed under a surface of the semiconductor substrate, a storage layer formed on the semiconductor substrate, a gate stacked on the storage layer, wherein the first diffusion region may at least one of active regions being separated by a part of the semiconductor substrate forming a channel region., wherein the second diffusion region may include an active region intersecting the gate insulating layer, wherein the storage layer may include an insulating layer or a variable resistor, and may service as a data storage layer to store data, and may be selected by a structure including the first and the second diffusion regions.

BACKGROUND 1. Field

Embodiments of the inventive concept relate to a nonvolatile memorydevice and a method of fabricating the same and, more particularly, to anonvolatile memory device including a part of a transistor serving as abasic structure, an insulating layer or a variable resistor.

2. Description of Related Art

A conventional art disclosed in US Patent Publication No. 20130249017related a nonvolatile memory device and a method of fabricating thesame. The nonvolatile memory device includes a memory cell having atransistor in which an insulating isolation layer is formed in a channelregion. The nonvolatile memory device includes ametal-oxide-semiconductor (MOS) transistor as a basic component. Aninsulating isolation layer is formed in at least a channel region, and agate insulating layer includes an insulating layer or a variableresistor and serves as a data storage. A gate includes a metal layerformed in a lower portion thereof. A first source and a drain regionsare lightly doped with a dopant, and a second source and a drain regionsare heavily doped with a dopant. Alternatively, the nonvolatile memorydevice includes a MOS transistor serving as a basic component. The MOStransistor includes at least a channel region in which an insulatingisolation layer is formed, and a gate insulating layer includes aninsulating layer or a variable resistor and serves as a data storage. Agate includes a conductive layer, a first and a second source regionsform a diode, and a first and a second drain regions form a diode.

A conventional art disclosed in Korean Patent Publication No.2001-0056831 relates to a method of forming an anti-fuse of asemiconductor device, more specifically, a method of forming ananti-fuse of a semiconductor device, which may easily break aninsulating layer at a lower voltage using a right-angled corner of asemiconductor substrate. The disclosed method includes forming apredetermined pattern on a semiconductor substrate on which a processfor a lower structure is completely performed to form a structure havingright-angled corners, depositing a gate oxide layer and stacking anitride layer and a first polysilicon (poly-Si) layer on the gate oxidelayer, forming a photoresist pattern to expose the first poly-Si layerformed on the right-angled corners of the semiconductor substrate, dryetching the exposed first poly-Si layer to firstly expose the nitridelayer formed on the right-angled corners of the semiconductor substrate,dry etching the nitride layer, and depositing a second poly-Si layer andforming a pattern. In the above-described method of forming theanti-fuse of the semiconductor device, an anti-fuse capable of easilybreaking an insulating layer at a lower voltage may be fabricated.

Another conventional art disclosed in Korean Patent Publication No.1997-0067848 relates to a semiconductor memory device and a method offabricating the same. The semiconductor memory device includes an accesstransistor T configured to access information of word lines, a storagenode capacitor C configured to store information stored through a bitline due to an operation of the access transistor T, and a charge-uptransistor P configured to supply charges to the storage node capacitorC. In the above-described semiconductor memory device, charges may becontinuously supplied to the storage node capacitor C so that aprocessing speed of the semiconductor memory device can be improved.

Meanwhile, a nonvolatile semiconductor memory device may be asemiconductor memory device in which information stored in a memory cellis retained even if power supply is interrupted.

The nonvolatile memory device may be electrically programmed. Thenonvolatile memory device may include memory cells in which storagelayers include insulating layers or variable resistors.

When the storage layers include the insulating layers, a high voltagefor a program operation may be applied to both electrodes (i.e., a firstelectrode and a second electrode) between the insulating layers to causea breakdown. In this case, a resistive path may be generated so that theinsulating layers may be changed from an insulation state to aconduction state. Accordingly, the insulating layers may becomeanti-fuses. When the insulating layers are in the conduction state, thenonvolatile memory device may be in a programmed state, and theprogrammed state may be defined as storage of data ‘0.’ Also, when theinsulating layers are in the insulation state, the nonvolatile memorydevice may be in an unprogrammed state, and the unprogrammed state maybe defined as storage of data ‘1.’

Conversely, the conduction state may be defined as data ‘1,’ and theinsulation state may be defined as data ‘0.’

When the storage layers are the variable resistors, the variableresistors may include a resistance variable material or a phasetransition material.

In a case in which the variable resistors of the memory cell include theresistance variable material, when a voltage equal to or higher than aset voltage is applied to both electrodes (i.e., a first electrode and asecond electrode) between the variable resistors, the variable resistorsmay be put into a low resistance state, and when a voltage equal to orhigher than a rest voltage is applied to the first and the secondelectrodes between the variable resistors, the variable resistors may beput into a high resistance state. Accordingly, the low resistance statemay be defined as storage of data ‘0,’ and the high resistance state maybe defined as storage of data ‘1.’ Conversely, the low resistance statemay be defined as storage of data ‘1,’ and the high resistance state maybe defined as storage of data ‘0.’

The resistance variable material is being developed using variousmaterials, such as perovskite, transition metal oxides, andchalcogenides.

Memory devices using the resistance variable material may be classifiedinto several types according to materials. A first type is a memorydevice in which a colossal magnetoresistance (CMR) material, such asPr_(1-x)Ca_(x)MnO₃ (PCMO), is inserted between electrodes and avariation in resistance due to an electric field is used. A second typeis a memory device in which a binary oxide, such as niobium oxide(Nb₂O₅), titanium oxide (TiO₂), nickel oxide (NiO), or aluminum oxide(Al₂O₃), is prepared to have a nonstoichiometric composition and used asa resistance variable material. A third type is a memory device in whicha chalcogenide material maintains an amorphous structure and adifference in resistance due to a variation in the threshold voltage ofan ovonic switch is used, instead of supplying a large current to thechalcogenide material to change the phase of the chalcogenide materialas in a phase-change random access memory (PRAM). A fourth type is amemory device in which a ferroelectric material, such as strontiumtitanium oxide (SrTiO₃) or strontium zirconium oxide (SrZrO₃), is dopedwith chromium (Cr) or Nb to change a resistance state. A final type is amemory device including programmable metallization cells (PMCs) in whichsilver (Ag) having a high ion mobility is doped into a solidelectrolyte, such as germanium selenium (GeSe), so that two resistancestates are formed depending on whether or not a conductive channel isformed in a medium due to an electrochemical reaction. In addition,materials or fabrication processes capable of embodying two stableresistance states to obtain memory characteristics have been reported.

In a case in which the variable resistors of the memory cell include thephase transition material, when the phase transition material is in alow resistance state, the low resistance state may be defined as storageof data ‘0,’ and when the phase transition material is in a highresistance state, the high resistance state may be defined as storage ofdata ‘1.’ Conversely, the low resistance state may be defined as storageof data ‘1,’ and the high resistance state may be defined as storage ofdata ‘0.’

The phase transition material may be changed into a crystalline phase oran amorphous phase due to a predetermined current. The crystalline phasemay correspond to the low resistance state, and the amorphous phase maycorrespond to the high resistance state.

According to the conventional techniques, since a MOS transistor and astorage element should be formed in a memory cell, a fabrication processbecomes relatively intricate. Also, since a footprint of the memory cellis big, there is a fundamental limit to increasing the integrationdensity of memory devices.

SUMMARY

Embodiments of the inventive concept provide a memory cell capable ofstoring data smaller area to obtain a higher integration density than inthe conventional art. The memory cell includes a part of a transistorserving as a basic structure, a storage layer of an insulating layer ora variable resistor.

Other embodiments of the inventive concept provide methods of operatingand fabricating the memory cell.

Furthermore, other embodiments of the inventive concept provide a memoryarray including the memory cell, a semiconductor memory device includingthe memory array, and a method of operating the memory array. Also, itmay be easily understood that aspects and advantages of the inventiveconcept may be realized by units described in the claims andcombinations thereof.

The technical objectives of the inventive disclosure are not limited tothe above disclosure; other objectives may become apparent to those ofordinary skill in the art based on the following descriptions.

In accordance with an aspect of the inventive concept, a nonvolatilememory device includes a semiconductor substrate, a first and a seconddiffusion regions formed under a surface of the semiconductor substrate,a storage layer formed on the semiconductor substrate, a gate stacked onthe storage layer, wherein the first diffusion region may at least oneof active regions being separated by a part of the semiconductorsubstrate forming a channel region, wherein the second diffusion regionmay include an active region intersecting the gate insulating layer,wherein the storage layer may include an insulating layer or a variableresistor, and may service as a data storage layer to store data, and maybe selected by a structure including the first and the second diffusionregions.

The first diffusion region may include an active region intersecting agate sidewall spacer.

The memory cell may be configured with other memory cell by sharing atleast the first diffusion region.

The memory cell may be configured with other memory cell by sharing atleast the gate.

An insulating isolation layer may be formed between at least the seconddiffusion regions in the semiconductor substrate.

The first and the second diffusion regions may form a diode.

A third diffusion layer or buried oxide layer may be formed below thefirst diffusion region or the second diffusion region.

A fourth diffusion layer may be formed below the third diffusion layer.

The third diffusion region and the fourth diffusion region or thesemiconductor substrate may form a bipolar transistor.

A voltage or current, applied to the fourth diffusion layer or thesemiconductor substrate, is controlled for changing a current flowbetween the second diffusion region and the fourth diffusion region orthe semiconductor substrate.

The variable resistor may include a material with characteristics to below resistance state or high resistance state according to a voltage ora current applied thereto, for example, the variable resistor includes aphase change material, a resistance variable material, or a resistancevariable material by magnetic orientation, or may include a data storageelement of Phase Change Random Access Memory (PCRAM), Resistive RandomAccess Memory (ReRAM), or Magnetic Random Access Memory(MRAM), orMTJ(Magnetic Tunnel Junction).

A gate of one memory cell may in one direction and be shared with and bedirectly connected to a gate of another memory cell arranged in the onedirection without passing through a contact.

A contact hole may be formed in the storage layer.

The fourth diffusion layer may be separately formed according to data orbit lines.

A contact hole may be formed on the first diffusion region and the gate,and the contact hole is filled with a conductive material, and a storagelayer is additionally formed on the conductive material.

A contact hole may be formed on the storage layer, and the contact holemay be filled with a conductive material, and a storage layer may beadditionally formed on the conductive material, or further storagelayers repeatedly may be stacked by the same structure.

A top conductive layer may be formed on the storage layer and a bottomconductive layer may be formed under the storage layer.

The conductive material filled in the contact hole and the top and thebottom conductive layers can be merged into a conductive layer.

A voltage or a current, applied to the fourth diffusion region, isvaried according to data.

A set or reset is operated by applying to the diode with a reverse biasto make a diode breakdown.

Data may be stored according to with or without formation of the contacthole in the storage layer. Thus, Read Only Memory (ROM) may be formed bya mask determining the formation of the contact hole in the storagelayer.

A first diffusion electrode connected to the first diffusion region maybe connected to a bit line, or the first diffusion electrode may beconnected to the word line.

A method of fabricating a nonvolatile memory device includes or forminga first, second diffusion layer in a semiconductor substrate, forming astorage layer on the semiconductor substrate.

The method of fabrication may include further forming a contact hole inthe storage layer and filling the contact hole with a conductivematerial.

In accordance with an aspect of the inventive concept, the method offabrication may include further forming a third diffusion region in thesemiconductor substrate or forming a third and a fourth diffusion regionin the semiconductor substrate.

Specific particulars of other embodiments are included in detaileddescriptions and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the inventiveconcepts will be apparent from the more particular description ofpreferred embodiments of the inventive concepts, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the inventive concepts. In the drawings:

FIG. 1A is a cross-sectional view of a memory cell according to anembodiment of the inventive concept;

FIG. 1B is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 1C is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 1D is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 1E is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 1F is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 2A is a cross-sectional view of two memory cells according toanother embodiment of the inventive concept;

FIG. 2B is a cross-sectional view of two memory cells according toanother embodiment of the inventive concept;

FIG. 2C is a cross-sectional view of a memory cell according to anotherembodiment of the inventive concept;

FIG. 3 is a cross-sectional view of four memory cells according toanother embodiment of the inventive concept;

FIG. 4A is a cross-sectional view illustrating preparation of asemiconductor substrate with a fourth diffusion region to fabricate amemory according to an embodiment of the inventive concept;

FIG. 4B is a cross-sectional view illustrating formation of aninsulating isolation layer to fabricate a memory according to anembodiment of the inventive concept;

FIG. 4C is a cross-sectional view illustrating formation of a thirddiffusion region to fabricate a memory according to an embodiment of theinventive concept;

FIG. 4D is a cross-sectional view illustrating formation of a seconddiffusion region to fabricate a memory according to an embodiment of theinventive concept;

FIG. 4E is a cross-sectional view illustrating formation of a storage, agate, and sidewall spacers to fabricate a memory according to anembodiment of the inventive concept;

FIG. 4F is a cross-sectional view illustrating formation of a firstdiffusion region to fabricate a memory according to an embodiment of theinventive concept;

FIG. 4G is a cross-sectional view illustrating formation of a contacthole to fabricate a memory cell according to an embodiment of theinventive concept;

FIG. 4H is a cross-sectional view illustrating filling the contact holewith a conductive material to fabricate a memory cell according to anembodiment of the inventive concept;

FIG. 5 is a circuit diagram of a memory cell according to an embodimentof the inventive concept;

FIG. 6A is a circuit diagram of a memory cell according to anotherembodiment of the inventive concept;

FIG. 6B is a circuit diagram of a memory cell according to anotherembodiment of the inventive concept;

FIG. 7 is a circuit diagram of a memory cell according to anotherembodiment of the inventive concept;

FIG. 8A is a layout of a memory array—A according to an embodiment ofthe inventive concept;

FIG. 8B is a layout of a memory array—A according to another embodimentof the inventive concept;

FIG. 8C is a layout of a memory array—A according to another embodimentof the inventive concept; and

FIG. 9 is a construction diagram of the entire memory device accordingto an embodiment of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinventive concept are shown. This inventive concept may, however, beembodied in different forms and should not be construed as limited tothe embodiments set forth herein. Rather, these embodiments are providedso that this disclosure is thorough and complete and fully conveys thescope of the inventive concept to one skilled in the art.

The following detailed description is merely exemplary in nature and isnot intended to limit the application and uses contemplated herein.Furthermore, there is no intention to be bound by any theory presentedin the preceding background or the following detailed description.

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinventive concept are shown.

A structure according to the inventive concept may be formed on asemiconductor substrate including a bulk silicon wafer or a silicon thinlayer disposed on an insulating layer (typically referred to as asilicon-on-insulator (SOI)).

Hereinafter, a state in which a resistive path is not present in astorage layer of a memory cell will be defined as data ‘0,’ and a statein which the resistive path is formed in the storage of the memory cellwill be defined as data ‘1.’ The inventive concept is not limitedthereto. For example, the state in which the resistance path is notpresent will be defined as data ‘1,’ and the state in which theresistance path is formed will be defined as data ‘0.’

FIG. 1A is a cross-sectional view of a memory cell 250 according to anembodiment of the inventive concept.

FIG. 5 is a circuit diagram of the memory cell 250 shown in FIG. 1A,according to an embodiment of the inventive concept.

As shown in FIG. 1A, the memory cell 250 according to the embodiment ofthe inventive concept may include a part of a transistor.

The memory cell 250 shown in FIG. 1A may include a MOS transistorsimilar to a typical MOS transistor as a basic component. Specifically,the memory cell 250 may include a fourth diffusion region 215, a storagelayer 235 on a semiconductor substrate, a gate 240 stacked on thestorage layer 235, a gate electrode GG connected to the gate 240,sidewall spacers 225 formed on sidewalls of the gate 240, a firstdiffusion region 226, and a first diffusion electrode DD connected tothe first diffusion region 226.

Although the present embodiment pertains to an example in which sidewallspacers are formed, the inventive concept is not limited thereto and maybe applied to a modified example in which sidewall spacers are notformed.

As shown in FIG. 1A, the first diffusion region 226 is at least one ofactive regions being separated by a part of the semiconductor substrateforming a channel region. The second diffusion region 216 may refer to aregion of an active region, which may intersect the storage layer 235 orthe sidewall spacers 225. The second diffusion region 216 may be dopedwith a complementary dopant to the first diffusion region. Thus thefirst and the second diffusion regions 226, 216 may form a diode.

As shown in FIG. 1A, a third diffusion region 266 or a buried oxide 226may be formed below the first and the second diffusion layer 226, 216.The third diffusion region 266 may be doped with a similar dopant to thefirst diffusion region 266.

Although in the case that the buried oxide is formed, the memory cellmay be formed on a semiconductor substrate including a SOI instead of asemiconductor substrate including a bulk silicon wafer, the inventiveconcept is not limited to the semiconductor substrate including the SOI.

A fourth diffusion region 215 may be formed the semiconductor substrate215 may be below the third diffusion region 266 or the buried oxide 266.The fourth diffusion region 215 or the semiconductor substrate 215 maybe doped with a complementary dopant to the third diffusion region 266.Thus the second diffusing region, 216 the third diffusion region 266 andthe fourth diffusion region 215 or the semiconductor substrate 215 mayform a bipolar transistor.

The diode or the bipolar transistor may be an element to select thestorage layer.

The gate 240 may be the metal layer, and the storage layer 235 mayinclude an insulating layer or a variable resistor and serve as a datastorage.

As shown in FIG. 1A, the storage layer 235 between the gate 240 and thesecond diffusion region 217 may serve as a storage configured to storedata and be separately illustrated with a dotted ellipse 276 forclarity.

As shown in FIG. 1A, the gate 240 may include a conductive layer formedof a metal, a silicide, a metal compound, or poly crystalline silicon(poly-Si). Like a typical transistor, the gate 240 may include aconductive layer formed of poly-Si.

In FIG. 1A, the fourth diffusion region 215 may be typically doped witha P-type or N-type dopant.

In an embodiment of the inventive concept, it is assumed that the fourthdiffusion region 215 is an N type. Accordingly, the first and the thirddiffusion region 226, 266 may become an P-type semiconductor that isdoped with a complementary dopant to the fourth diffusion region 215 orthe semiconductor substrate 215, and the second diffusion region 216 maybecome an N-type semiconductor that is doped with a dopant similar tothe fourth diffusion 215 or the semiconductor substrate 215.

The first and the second diffusion regions 226, 216 may be formed of,for example, a P-type semiconductor and an N-type semiconductor,respectively, and constitute a PN junction diode structure. Conversely,the first and the second diffusion regions 226,216 may be formed of anN-type dopant and a P-type dopant, respectively, and constitute a PNjunction diode structure.

As is widely known to one skilled in the art, when a lightly dopedsemiconductor is in contact with a metal, a Schottky diode may beformed.

Furthermore, in another embodiment of the inventive concept, the firstand the second diffusion region 226, 217 may be formed of asemiconductor lightly doped with a similar dopant each other, the firstdiffusion electrode DD connected to the first diffusion region may beformed of silicide or a metal, and Schottky diode structures may beformed.

Referring to FIG. 1A, according to an embodiment of the inventiveconcept, the first and the second diffusion region 226, 216 may beformed of a semiconductor and a metal, respectively, and form a Schottkydiode. That is, the second diffusion region 216 may be formed of asemiconductor lightly doped with a dopant, and the first diffusionregion 226 may be formed of silicide. Conversely, the first and thesecond diffusion regions 226 and 216 may be formed of a metal and asemiconductor, respectively, and form a Schottky diode.

The formation of the diode structure according to the present inventionis not limited to the above description.

In another embodiment of the inventive concept, a contact hole may beformed in the storage layer and may be filled with a conductivematerial.

As compared with FIG. 1A, FIG. 1B shows a case in which a contact holeis formed in the storage layer 235 and is filled with a conductivematerial. If the conductive material is used the same as the gate, itcan be a buried contact for simplified fabrication.

The storage layer has a similar effect with a low resistance state bythe conductive material. Thus, the storage layer 235 stores data ‘1’. Astorage stores data ‘0’ if the storage layer has a high resistance statebecause there is no the contact hole in the storage layer. It may beconverted to mask Read Only Memory (ROM) by comprising the memory cellwithout the contact hole shown in FIG. 1A and the memory cell with thecontact hole 299 shown in FIG. 1B.

In another embodiment of the inventive concept, a contact hole may beformed on the first diffusion region and the gate, and the contact holemay be filled with a conductive material, and a storage layer may beadditionally formed on the conductive material.

As compared with FIG. 1B, FIG. 1C shows a case in which a storage layer237 with a top and bottom electrodes 242, 212 is additionally formed.The storage layer 237 places between the top and bottom electrodes 242,212. The top electrode 242 is connected to MM0 and the bottom electrode212 is connected to a contact hole 199 connected to a first diffusionregion 226. The contact hole 199 is many level of contact holes stackedto connect with many level of conductive layers.

As compared with FIG. 1B, FIG. 1D shows a case in which a storage layer237 with a top and bottom electrodes 242, 212 is additionally formed.The storage layer 237 places between the top and bottom electrodes 242,212. The top electrode 242 is connected to MM0 and the bottom electrode212 is connected to a contact hole 399 connected to a gate 240. Thecontact hole 399 is many level of contact holes stacked to connect withmany level of conductive layers.

In another embodiment of the inventive concept, a contact hole may beformed on the storage layer, and the contact hole may be filled with aconductive material, and a storage layer may be additionally formed onthe conductive material, or further storage layers repeatedly may bestacked by the same structure.

As compared with FIG. 1D, FIG. 1E show a case in which a storage layer239 with a top and bottom electrodes 244, 214 is additionally formed.The storage layer 239 places between the top and bottom electrodes 244,214. The top electrode 242 is connected to MM1 and the bottom electrode214 is connected to a contact hole 499 connected to a top electrode 242on a storage layer 237 240. The contact hole 499 is many level ofcontact holes stacked to connect with many level of conductive layers.The further storage layer with the top and bottom electrodes may berepeatedly formed as the above description. A repeated descriptionthereof is omitted for brevity.

In accordance with an aspect of the inventive concept, a contact holemay be formed on the storage layer, and the contact hole may be filledwith a conductive material, and a storage layer may be additionallyformed on the conductive material, or further storage layers repeatedlymay be stacked by the same structure.

As compared with FIG. 1B, FIG. 1F shows a case in which a storage layer835 is additionally formed on a storage layer 235 and a contact hole299.

There are several configurations to form an array with memory cells.

In an embodiment of the inventive concept, the memory cell and adjacentmemory cell may share at least its first diffusion region. Theseembodiments are shown in FIG. 2A. As shown in FIG. 2A, a first, third,and fourth diffusion regions 228, 268, 215 are shared. As shown in FG2A, a first diffusion electrode DD is connected to the shared firstdiffusion region, there are gate electrodes GG0, GG1 and storage layers235. As shown in FIG. 2A, the storage layers 235 as storages configuredto store data are separately illustrated with a dotted ellipse 276, 277for clarity.

Furthermore, in another embodiment of the inventive concept, the memorycell and adjacent memory cell may share at least its gate and storagelayer. These embodiments are shown in FIG. 2B. As shown in FIG. 2B, agate 240 and a storage layer 235 are shared.

As shown in FIG. 2B, a gate electrode GG is connected to the sharedgate, there are first diffusion electrodes DD0, DD1 and storage layer235. There is an insulating isolation layer 210 between second diffusionregions 216, 217 and between third diffusion regions 266, 267. Referringto FIG. 2B, unlike a typical transistor, the first electrodes DD0, DD1may be disconnected each other due to an electrical isolation functionof the insulating isolation layer 210 shown in FIG. 2B. As shown in FIG.2B, the storage layers 235 as storages configured to store data areseparately illustrated with a dotted ellipse 276, 277 for clarity.

As compared with FIG. 2A, FIG. 2C shows one memory cell with aninsulating isolation layer 212.

As compared with FIG. 2A, FIG. 3 shows two FIG. 2A with different fourthdiffusion regions.

Since the above-described modified embodiments may be easily understoodby one skilled in the art, a detailed description thereof will beomitted here. However, the present inventive concept should beinterpreted as including various modified embodiments.

A method of fabricating a nonvolatile memory device according to theinventive concept may include forming a first, second diffusion layer ina semiconductor substrate, forming a storage layer on the semiconductorsubstrate.

The method of fabricating the memory device according to the inventiveconcept may include further forming a contact hole in the storage layerand filling the contact hole with a conductive material.

The method of fabricating the memory device according to the inventiveconcept may Include further forming a third diffusion region in thesemiconductor substrate or forming a third and a fourth diffusion regionin the semiconductor substrate.

Various process operations for fabricating typical MOS transistors arewidely known. Accordingly, conventional process operations will bebriefly described for clarity, or some known processes will be whollyomitted.

A method of fabricating a memory device according to an embodiment ofthe inventive concept is illustrated in FIGS. 4A through 4E.

The method of fabricating the memory cell according to the embodiment ofthe inventive concept may start from an operation of preparing asemiconductor substrate with a fourth diffusion region 215 as shown inFIG. 4A.

The semiconductor substrate may be a single crystalline siliconsubstrate. Although the present embodiment pertains to an example inwhich a bulk silicon wafer is used, the inventive concept is not limitedthereto.

The fourth diffusion region 215 may be a P-type well doped with a P-typedopant or an N-type well doped with an N-type dopant. In the presentembodiment, it is assumed that the fourth diffusion region 215 is theN-type well doped with the N-type dopant.

Thereafter, referring to FIG. 4B, an insulating isolation layer 210 maybe formed. The insulating isolation layer 210 may be formed using atypical shallow trench isolation (STI) technique. In this case, theinsulating isolation layer 210 may be formed without forming anadditional mask.

The formation of the insulating isolation layer 210 may include formingtrenches by etching the surface of the semiconductor substrate 215 andfilling the trenches with an insulating material. After filling thetrenches with the insulating material, the resultant structure may beplanarized using, for example, a chemical mechanical polishing (CMP)process.

Thereafter, as shown in FIG. 4C, a third diffusion region 269 and may beformed. As described above, the third diffusion region 269 may be dopedusing a dopant that is complementary to the fourth diffusion region 215.Therefore, the third diffusion 269 may be a P-type semiconductor.Accordingly, a P-type dopant may be implanted into the third diffusionregion 269 in the arrow direction shown in FIG. 4C.

The third diffusion region 269 may be implanted with ions to have about1 to 1.5 times the depth of a first diffusion region to be subsequentlyformed. For example, when the first diffusion regions have a depth ofabout 0.2 μm, the third diffusion region 266 and 267 may have a depth ofabout 0.2 μm to about 0.3 μm.

Thereafter, as shown in FIG. 4D, a second diffusion regions 216, 217 maybe formed. As described above, the second diffusion regions 216, 217 maybe doped with a dopant that is complementary to the third diffusionregion 269. Therefore, the second diffusion regions 216, 217 may beN-type semiconductor. Accordingly, an N-type dopant may be implantedinto the second diffusion regions 216 and 217 in the arrow directionshown in FIG. 4D.

The second diffusion regions 216, 217 may be implanted with ions to haveabout 50%˜100% of the depth of the first diffusion regions to besubsequently formed. For example, when the first diffusion regions havea depth of about 0.2 μm, the second diffusion regions 216, 217 may havea depth of about 0.1˜0.2 μm. As described above, according toembodiments of the inventive concept, the second diffusion regions 216,217 may be implanted with ions in a self-aligned manner by theinsulating isolation layer 210. This is because the insulating isolationlayer 210 serves as an ion implantation mask.

The second diffusion regions 216, 217 may be ion-implanted in aself-aligned manner by the insulating isolation layer 210. This isbecause the insulating isolation layer 210 may serve as an ionimplantation mask.

The second diffusion regions 216, 217 may be formed before forming thegate. However, the inventive concept is not limited thereto. Forexample, like a typical lightly doped drain (LDD) structure, the seconddiffusion regions 216, 217 may be formed after forming the gate.

Thereafter, referring to FIG. 4E, the storage layer 235 may be stacked,and a gate including a metal layer 242 and a conductive layer 240stacked on the metal layer 242 may be formed on the gate insulatinglayer 235, and sidewall spacers 225 may be formed on sidewalls of thegate. Although the present embodiment pertains to an example in whichthe sidewall spacers 225 are formed, the inventive concept is notlimited thereto and may be applied to a modified example in whichsidewall spacers are not formed.

In an embodiment of the inventive concept, the gate insulating layer 235may be formed using a gate oxide layer, and the conductive layer 240 maybe formed of poly-Si.

The gate oxide layer may be formed by growing a thermal oxide layer onthe surface of the semiconductor substrate 215 or depositing an oxidelayer.

The gate oxide layer may have a thickness of about 1 nm to about 10 nm.The thickness of the gate oxide layer may be as thin as possible toreduce a voltage (VPP) for a program operation.

In another embodiment, the storage layer 235 may be formed using avariable resistor.

The storage layer 235 may be formed by stacking the variable resistor onthe surface of the semiconductor substrate to a predetermined thicknessinstead of an oxide layer. The variable resistor may be a compound layerformed by stacking various materials.

The variable resistor may be a resistance variable material, a phasetransition material, or another material having memory characteristicscapable of two stable resistance states.

The resistance variable material may be one of various materials, suchas perovskite, a transition metal oxide, or a chalcogenide. Theresistance variable material may be a material whose electricalresistance is changed into a low resistance state or a high resistancestate due to a predetermined voltage. The resistance variable materialmay be any one of a binary transition metal oxide and a tertiarytransition metal oxide or a combination thereof. The binary transitionmetal oxide may be TiO₂, NiO, HfO₂, Al₂O₃, ZrO₂, ZnO, Ta₂O₅, or Nb₂O₅,and the tertiary transition metal oxide may be SrTiO₃, HfAlO, HfSiO, orHfTiO.

Furthermore, the resistance variable material may be any one of copper(Cu)-doped SiO₂, silver (Ag)-doped SiO₂, a Cu-dopedgermanium-selenium-tellurium (Ge—Se—Te) compound, an Ag-doped Ge—Se—Tecompound, and a CuO_(x)-based resistance variable material or acombination thereof.

The phase transition material may be a material that is changed into acrystalline phase or an amorphous phase due to a predetermined current.A chalcogenide-based compound may be used as the phase transitionmaterial. The chalcogenide-based material having phase transitioncharacteristics may be a binary compound, a tertiary compound, or aquaternary compound, which includes a combination of at least two of Ge,Te, antimony (Sb), indium (In), Se, and tin (Sn), or the binary,tertiary, or quaternary compound to which bismuth (Bi) is added. Thephase transition material may be Ge₂Sb₂Te₅, or Ge₂Sb₂Te₅ into which anyone of nitrogen (N), oxygen (O), SiO₂, and Bi₂O₃ is doped, or acombination thereof.

As shown in FIG. 4E, a gate 240 may be deposited using poly-Si on thestorage layer 235, and the conductive layer 240 formed of poly-Si may bepatterned using etching and photolithography processes.

After the patterning process, heat may be applied in an oxidationatmosphere so that a silicon oxide thin layer (not shown) can bethermally grown on sidewalls of the gate 240 and 242 to form sidewallspacers 225.

Thereafter, as shown in FIG. 4F, a dopant may be implanted in the arrowdirection to form a first diffusion region 226, 227.

Since the first diffusion regions 226, 227 should be doped with a dopantthat is complementary to the second diffusion regions 216, 217, a P-typedopant may be ion-implanted into the first diffusion regions 226, 227 inthe present embodiment.

According to an embodiment of inventive concept, the method offabricating a nonvolatile memory device includes further forming acontact hole in the storage layer and filling the contact hole with aconductive material.

The embodiment is shown in FIGS. 4G, 4H. As shown in FIG. 4G, after thegate oxide layer is formed, a contact hole 699 may be formed. Thecontact hole 699 is desirable to be formed by oxide etching process.Filling the contact hole 699 with a conductive material is subsequentafter forming the contact hole. As shown in FIG. 4H, a gate 240 may beformed by filling the contact hole 699 with a conductive material andsimultaneously depositing the conductive material on the gate oxide.

As shown in FIG. 4H, a left first diffusion region 216 is connected tothe gate via the formation of the contact hole. Thus, data ‘0’ isstored. Aright second diffusion 217 region is not connected to the gatebecause of no formation of the contact hole. Thus, data ‘1’ is stored.Accordingly it may be converted to Read Only Memory (ROM) by thefabrication with a mask determining the formation of the contact hoe inthe storage layer.

Finally, the fabrication of the memory according to the inventiveconcept may be completed by known process operations (not shown) of, forexample, depositing a dielectric material layer, etching openingsthrough the dielectric material layer to expose portions of the firstdiffusion region, and forming metalized portions to extend through theopenings and be electrically connected to the first diffusion region.

FIG. 5 is an equivalent circuit diagram of the memory cells shown inFIG. 1A, according to an embodiment of the inventive concept, and FIG.6A is an equivalent circuit diagram of the memory cell shown in FIG. 2A,and FIG. 6B is an equivalent circuit diagram of the memory cell shown inFIG. 2B. An equivalent circuit of the memory cell shown in FIG. 6B isomitted because it would be easily understood with reference to FIGS. 2Aand 6A.

In accordance with an aspect of the inventive concept, the second, thirddiffusion regions and the fourth diffusion region or the semiconductorsubstrate may form a bipolar transistor

As shown in 5, a storage layer 235 shown in FIG. 1A may be simplyrepresented as a variable resistor 276 because it is an insulating layeror a variable resistor layer. In FIG. 1A, an embodiment of the inventiveconcept is a case with a third diffusion region, instead of buried oxidelayer. A diode structure between a first, third diffusion regions 226,266 and a second diffusion 216 in FIG. 1A may be represented as a firstdiode 286 in FIG. 5. A diode structure between a first, third diffusionregions 226, 266 and a fourth diffusion 215 in FIG. 1A may berepresented as a second diode 296 in FIG. 5. The first and the seconddiodes 286, 296 may be a bipolar transistor.

Typically, when the storage layer 235 is an oxide layer, a VCC voltagemay be adjusted such that an electric field of about 5 MV/cm is appliedto the oxide layer 235. Also, to cause a gate breakdown in the oxidelayer 235 and generate a resistive path, a VCC voltage may be adjustedsuch that an electric field of about 20 MV/cm is applied to the oxide235.

For example, assuming that the gate insulting layer has a thickness ofabout 2.3 nm in a process using a gate length of about 130 nm, a VCCvoltage may be about 1.2 V, and a VPP voltage required for generating aresistive path may be about 5 V.

Accordingly, in the above-described example, a VPP voltage for a programoperation may be about 6V considering a diode threshold.

Hereinafter, a case in which the storage layer 235 is an insulatinglayer will be referred to as an A type, and a case in which the gateinsulating layer 235 is a variable resistor will be referred to as a Btype.

A nonvolatile memory including an A-type memory cell and a method ofoperating the same may be similar to a nonvolatile memory including aB-type memory cell and a method of operating the same except that, inthe A-type memory cell, a gate insulating layer serving as a storagelayer is difficult to be changed from a low resistance state (LRS) intoa high resistance state (HRS), unlike a variable resistor. Thus, sincethe above-described circuit and operation of the memory device includingthe A-type memory cell according to an embodiment of the inventiveconcept may be easily applied to a circuit and operation of a memorydevice including a B-type memory cell, a repeated description will beomitted for brevity.

For example, the above-described VPP voltage, which is a programvoltage, may be a voltage required to generate a resistive path in agate insulating layer and send the gate insulating layer from a highresistance state (HRS) into a low resistance state (LRS).

Similarly, a set voltage may change a variable resistor from a highresistance state (HRS) into a low resistance state(LRS).

Accordingly, the VPP voltage serving as the program voltage may beadjusted to be the set voltage (VSET) for the variable resistor, and aprogram operation may be performed in a similar manner to the case inwhich the memory device includes the A-type memory cell.

Furthermore, the VPP voltage, which is the program voltage, may beadjusted to be a reset voltage(VRESET) and send the variable resistorfrom a low resistance state(LRS) into a high resistance state(HRS).

But, in bipolar switch case, a voltage polarity across the variableresistor for set should is reverse with a voltage polarity for reset.

According to the inventive concept. A voltage or current, applied to thefourth diffusion layer or the semiconductor substrate, may be controlledfor changing current flow between the second diffusion region and thefourth diffusion region or the semiconductor substrate.

A set and reset operation of a memory according to an embodiment of theinventive concept will described in the case that a storages layeroperate with bipolar switching.

In the case of using a diode for bipolar switching bias across thestorage layer according to another embodiment of the inventive concept,a set or reset may be operated by applying to the diode with a reversebias to make a diode breakdown.

According to the inventive concept, a voltage or current may bedifferently applied to the fourth diffusion region according to data.

FIG. 7 is an equivalent circuit diagram of the memory cells shown inFIG. 3.

As shown in FIG.7, four memory cells are illustrated. Set and resetsimultaneously may operate in memory cells. When 0V and VRESET voltageare applied to gates GG0, GG2, respectively, and VSEL voltage is appliedto a first diffusion electrodes DD0, DD1, and VSET voltage, 0V areapplied to a fourth diffusion electrodes SB0, SB1, respectively, a NPNbipolar transistor including a first and a second diodes 286, 296 is inoperating condition. Thus, the current of the bipolar transistor flowstoward GG0, and VSET voltage with dropped diode threshold voltage acrossa first storage layer is applied. Therefore, the first storage layer 276is in a Low Resistance state (LRS).

Another NPN bipolar transistor including the first and the second diodes387, 397 is in operating condition. Thus, the current of the bipolartransistor flows toward SB1, and VRESET voltage with dropped diodethreshold voltage across a second storage layer 297 is applied withopposite current flow of set. Therefore, the third storage layer 376 isin High Resistance State (HRS).

In FIG. 7, read may operate. When 0V voltage is applied to gates GG0,GG2, and VCC voltage is applied to first diffusion electrodes DD0, DD1,and fourth diffusion electrodes SB0, SB1, a NPN bipolar transistorincluding a first and a second diodes 286, 296 is in operating conditionand the first storage layer 276 is in Low Resistance State (LRS). Thus,the current flows toward GG0. But the third storage layer 376 is in HighResistance State (HRS). Thus, the current doesn't flow toward GG2.

Accordingly, the resistance state of the storage layer can be convertedto digital signal through a read circuitry to sense the current.

As described above, there are two methods for connecting word lines andbit lines in the memory cell 250. In a first method, a gate electrode GGmay serve as a word line, each of a first diffusion electrode DD mayserve as a bit line.

In a second method, as opposed to the first method, a gate electrode GGmay serve as a bit line, a first diffusion electrode DD may serve as aword line.

FIG. 8A illustrates the layout of a memory array according to anembodiment of the inventive concept.

In FIG. 8A, the layout of the two memory cells 550 is separatelyillustrated with a dotted square.

A cross-sectional view of the two memory cells 550, which is taken alongline A-A′ of FIG. 8A, is the same as in FIG. 2A except for a contact 366to be connected to a word line WL2 and the word line WL2.

As shown in FIG. 8A, the two memory cells 550 may be arranged in amatrix shape. In this case, the two memory cells 550 may not becontinuously arranged but may be alternately arranged in every other rowand in every other column. That is, the two memory cells 550 may bedisposed in a pattern similar to a check board.

When the two memory cells 550 are instead continuously arranged, a bitline may be shared between two memory cells, so that data of the twomemory cells may collide in the shared bit line. To prevent thisproblem, the two memory cells 550 may be arranged as shown in FIG. 8A.

Referring to FIG. 8A, word lines WL0, WL1, WL2, . . . may run in an Xdirection, and bit lines BL0, BL1, BL2, . . . may run in a Y direction.Active regions 412, 420, 424, and 432 may include regions in whichspaces between the bit lines BL0, BL1, BL2, . . . intersect the wordlines WL0, WL1, WL2, . . . .

The active regions are connected the world lines and the remainingregion of the active regions is corresponding to a shallow trenchisolation (STI) region.

As shown in FIG. 8A, regions 362 and 364 in which an active region 420intersects bit lines BL0, BL1 may be a second diffusion region and areseparately striped for clarity.

The inventive concept is characterized in that a gate of one memory cellmay run in one direction and be shared with and be directly connected toa gate of another memory cell arranged in the one direction withoutpassing through a contact.

For example, referring to FIG. 8A, a gate BL2 of a memory cell having aseconding diffusion region 324 may run in a lengthwise direction and beshared with and be directly connected to a gate BL2 of a memory cellhaving a second diffusion region 344 adjacent thereto in the lengthwisedirection.

Since the gate of adjacent memory cells may be directly connectedwithout passing through a contact, a horizontal area of a memory arraymay be reduced.

FIG. 8B illustrates the layout of a memory array according to anotherembodiment of the inventive concept.

In FIG. 8B, the layout of the two memory cells 550 is separatelyillustrated with a dotted square.

A cross-sectional view of the two memory cells 550, which is taken alongline A-A′ of FIG. 8B, is the same as in FIG. 2A except for a contact 366to be connected to a word line WL2 and the word line WL2.

As shown in FIG. 8B, the two memory cells 550 may be arranged in amatrix shape. In this case, the two memory cells 550 may be arranged inevery row and in every other column. The two memory cells 550 arearranged as shown in FIG. 8B for the same reason as described above.

Since the layout of the memory array of FIG. 8B is similar to that ofthe memory array of FIG. 8A, a repeated description thereof is omittedfor brevity.

FIG. 8C illustrates the layout of a memory array according to anotherembodiment of the inventive concept.

In FIG. 8C, the layout of a memory cell 558 is separately illustratedwith a dotted square.

A cross-sectional view of the memory cell 558, which is taken along lineB-B′ of FIG. 8C, is the same as in FIG. 2C except for a contact 366 tobe connected to a word line WL2 and the word line WL2.

As shown in FIG. 8C, the memory cells 558 may be arranged in a matrixshape. In this case, one bit line may intersect a gate in each of thememory cells 558 so that each of the memory cells 558 may have onestorage region.

FIG. 9 shows the overall configuration of a memory device according toan embodiment of the inventive concept.

The overall memory device according to the inventive concept may includea memory array in which a plurality of memory cells are arranged, aninternal supply unit configured to generate a voltage VSET, VRESET andVSB used for the memory array, a row decoder configured to select a wordline from the memory array, a column decoder configured to select a bitline, a write circuit configured to receive a data bus from aninput/output (I/O) unit and transmit the data bus to a global bit linebus GBL under the control of a controller, a read circuit required for aread operation including transmitting stored data to the global bit linebus GBL, sensing and amplifying an electrical state of the global bitline bus using a sense amplifier, converting the sensed and amplifiedelectrical state into a digital signal, and transmitting the digitalsignal to the I/O unit, a controller configured to control the inside ofthe memory device, and the I/O unit configured to allow the outside ofthe memory device to interface with the inside of the memory device.

The configuration of the memory device will now be briefly described.The memory device may include the above-described memory array 140 andan internal supply unit 110 configured to generate the voltage VSET,VRESET, and VSB required for set and reset operation.

Furthermore, the memory device may include the row decoder 150configured to select a word line form the memory array 140 and thecolumn decoder 160 configured to select a bit line.

Referring to FIG. 9, the row decoder 150 and the column decoder 160 mayreceive an address bus from the I/O unit 130, be controlled by acontroller 120, and decode an address.

The memory device may include the write circuit 170 used for a datawrite operation. The write circuit 170 may receive the data from the I/Ounit 130 and transmit the data to the global bit line bus GBL (GBL0,GBL1, GBL2, . . . ) under the control of the controller 120.

Referring to FIG. 9, the memory device may include a read circuit 180required for a data read operation. Stored data may be transmitted tothe global bit line bus GBL (GBL0, GBL1, GBL2, . . . ), and a senseamplifier 181 in the read circuit 180 may sense and amplify anelectrical state of the global bit line bus GBL, convert the sensed andamplified electrical state into a digital signal, and transmit thedigital signal to the I/O unit 130.

The I/O unit 130 may allow the outside of the memory device to interfacewith the inside thereof. The controller 120 may receive commandsrequired for the write and read operations from the I/O device 130,analyze the commands in detail, and control circuits related with thecommands.

Construction of the memory device according to the embodiment of theinventive concept may be modified. For example, the memory device is notlimited to a one-time programmable (OTP) device and a multi-timeprogrammable (MTP) device and may be used for a storage device storinginformation on a redundancy repair including a fuse, which may be usedin various semiconductor devices, such as a dynamic random access memory(DRAM) or a static random access memory (SRAM). Also it may be used fora storage device storing information required for programmable logicdevice (PLD) and field programmable gate array(FPGA).

The foregoing is illustrative of embodiments and is not to be construedas limiting thereof. Although a few embodiments have been described,those skilled in the art will readily appreciate that many modificationsare possible without materially departing from the novel teachings andadvantages. Accordingly, all such modifications are intended to beincluded within the scope of this inventive concept as defined in theclaims. In the claims, means-plus-function clauses are intended to coverthe structures described herein as performing the recited function, andnot only structural equivalents but also equivalent structures.

1. A semiconductor device comprising: a plurality of memory cells,wherein a memory cell of the plurality of the memory cells, comprising:a semiconductor substrate; a storage layer formed on the semiconductorsubstrate; a first diffusion region formed in the semiconductorsubstrate on one side of the storage layer; and a second diffusionregions formed in the semiconductor substrate under the storage layer;and a gate stacked on the storage layer, wherein the storage layerincludes an insulating layer or a variable resistor, and wherein thefirst diffusion region is formed apart from the storage layer.
 2. Thedevice of claim 1, wherein further comprising: a sidewall spacer formedalong laterally sidewall of the gate, wherein the sidewall spacer isformed on a portion of the second diffusion region.
 3. The device ofclaim 1, wherein the plurality of the memory cells is configured toshare the first diffusion region of the memory cell.
 4. The device ofclaim 1, wherein the plurality of memory cells is configured to sharethe gate of the memory cell.
 5. The device of claim 4, wherein thedevice further comprising: an insulating isolation layer is formedbetween the second diffusion regions of the plurality of memory cells.6. The device of claim 1, wherein the first diffusion region and thesecond diffusion regions form a diode.
 7. The device of claim 1, whereinthe device further comprising: a third diffusion layer or a buried oxidelayer is formed below the second diffusion region.
 8. The device ofclaim 7, wherein the device further comprising: a fourth diffusion layeris formed below the third diffusion layer.
 9. The device of claim 8,wherein the second, third diffusion regions and the fourth diffusionregion form a bipolar transistor.
 10. The device of claim 9, wherein avoltage or current applied to the fourth diffusion layer is controlledfor changing a current flow between the second diffusion region and thefourth diffusion region.
 11. The device of claim 1, wherein the variableresistor includes a material with characteristics to be in lowresistance state or high resistance state by a voltage or a current, forexample, the variable resistor includes a phase change material, aresistance variable material, or a resistance variable material bymagnetic orientation, or includes a data storage element of Phase ChangeRandom Access Memory(PCRAM), Resistive Random Access Memory(ReRAM), orMagnetic Random Access Memory(MRAM), or MTJ(Magnetic Tunnel Junction).12. The device of claim 1, wherein the gate of one memory cell runs inone direction and is shared with and is directly connected to a gate ofanother memory cell arranged in the one direction without passingthrough a contact.
 13. The device of claim 1, wherein the device furthercomprising: a contact hole is formed in the storage layer.
 14. Thedevice of claim 8, wherein the plurality of the memory cells isconfigured to share the fourth diffusion layer if the plurality of thememory cells shares the same data or bit lines.
 15. The device of claim1, wherein the device further comprising; a contact hole is formed onthe first diffusion region and/or the gate, and the contact hole isfilled with a conductive material, and a storage layer is additionallyformed on the conductive material.
 16. The device of claim 15, wherein athe contact hole is formed on the storage layer, and the contact hole isfilled with a conductive material, and a storage layer is additionallyformed on the conductive material, or further storage layers repeatedlyare stacked by the same structure.
 17. The device of claim 15, whereinthe device further comprising: a top conductive layer is formed on thestorage layer and a bottom conductive layer is formed under the storagelayer.
 18. The device of claim 15, wherein the conductive materialfilled in the contact hole and the top and the bottom conductive layersare merged into a conductive layer.
 19. The device of claim 8, wherein avoltage or a current, applied to the fourth diffusion region, is variedaccording to data.
 20. The device of claim 6, wherein a set or a resetare operated by applying to the diode with a reverse bias to make adiode breakdown.
 21. The device of claim 13, wherein data is storedaccording to with or without formation of the contact hole in thestorage layer.
 22. The device of claim 1, wherein the device furthercomprising: a first diffusion electrode connected to the first diffusionregion is connected to a bit line, or the first diffusion electrode isconnected to the word line. 23-25. (canceled)
 26. The device of claim22, wherein data is stored according to whether the first diffusionelectrode is connected to the bit line or not.
 27. The device of claim1, wherein the gate or the storage layer, and the second diffusionregion forms a diode when the storage layer is in resistance state.